A wide variety of lithographic technique have been employed to produce predefined patterns on the surfaces of many materials including resins, semiconductors, metals and paper. For many applications these techniques require complex machinery and processes. Some reproduction techniques, such as the types employed in the electronics industry for circuit manufacture, are quite costly and time consuming, thus requiring large scale production in order to be cost effective. This has placed severe constraints on efforts to evaluate new circuit concepts and test prototype circuit designs.
Numerous methods for depositing metal patterns on circuit structures have required costly preparation of photomasks. More recently, laser processes have been explored in an effort to deposit conductive material on insulating surfaces. See, for example, U.S. Pat. No. 4,496,607 to Mathias, which discloses use of a laser beam to melt tracks onto substrates into which conductive particles are simultaneously impinged. Because the method disclosed in the Mathias patent requires melting a trace into the substrate in order to fuse conductive particles in a pattern, the technique has limited utility when the surface material is subject to temperature constraints.
Processes for photochemical deposition have also been demonstrated with focused laser beams to "directly write" thin film patterns. Generally, decomposition techniques, e.g., laser induced chemical vapor deposition of metal films, are performed under partial vacuum conditions and require use of reactive gases. Many of these are serial deposition techniques and are therefore inherently slow in comparison to production oriented photolithography.
A paper by Higashi and Fleming, "Spatial Resolution Limits On Projection Patterned Photodeposited Conducting Aluminum Films" [Proceedings of Symposium D 1985 Fall Meeting of the Materials Research Society] published in Extended Abstracts Beam Induced Chemical Processes, 1985, suggests a solution to the speed limitations which have restricted the utility of this technique. The paper discloses a projection pattern technique wherein laser light is imaged through a photomask and onto a substrate which is positioned in a transparent cell. A gas such as trimethylaluminum is passed through the cell and decomposed to grow a pattern of aluminum. However, reported resistivities for room temperature depositions are in the range of 100 ohm-centimeters and increases in deposition cell temperature, while improving the conductive quality of the patterned layer, are accompanied by decreases in deposition rate, e.g., down to 0.4 Angstrom per second.
Generally, techniques which require subjecting the deposition surface to a partial vacuum are unsuitable for many applications due to the size or fragile nature of the surface.